Augmented and virtual reality are becoming a greater part of the computer user experience. Through augmented reality, a computer user wears a head mounted display that projects computer generated images onto a real-world scene, thus augmenting the scene with computer generated information. This information can be in the form of graphics or text. Cameras mounted on the head mounted display pick up the images of what the user is looking at in the real world. Virtual reality is similar to augmented reality except for the fact that the entire display that the user sees is generated by a computer; there are generally no cameras and no display of the local surroundings.
The head mounted display (“HMD”) usually contains two simple single element lenses, one for each eye, that focus on two respective flat panel displays. Each display is approximately two inches square and placed very close to the lenses and the user's eyes. Because of weight and size restrictions of HMDs only simple optical systems are practical. For example, the vast majority of commercially available HMDs use single element optical systems, although multiple element systems are possible. Simple optical systems have two primary lens aberrations that affect image quality: field curvature and chromatic aberration. Field curvature is a problem because a single element lens is really designed to clearly focus on a spherical surface; however, in an HMD they are focusing on a flat surface. Thus, one sees significant distortions or aberrations at the edges of the display. The second drawback of chromatic aberration is specifically lateral chromatic aberration that causes different wavelengths of light to have different magnifications. In other words, blue images will have a different magnification than red images or green images. So, it looks like there are three different slightly misaligned images in the display. Correcting for these aberrations is difficult.